New assist: add enum variant

[matklad]

It'd be cool if in this situation rust-analyzer realized that that what we want here is not a function, but a new error variant.

Looking at how generate function works should help with implementing this assist:

https://github.com/rust-analyzer/rust-analyzer/blob/5b9e46b960c37f04a26742c186e0a26b7bc131b3/crates/ide_assists/src/handlers/generate_function.rs

Note that generate function grew quite complex over time, for learning purposes, you might want to check some of its earlier versions

[zenofsahil]

I'd like to take a crack at this.

[maartenflippo]

@zenofsahil is this going well for you? This seems like an issue I would enjoy taking on as well, but obviously if you're still working on it I will find another (seems like there are plenty).

[zenofsahil]

@maartenflippo Thanks for checking! I was going through the codebase when some other priorities came up. I've been planning on coming back to this but it would be another couple of weeks before I can do that. Please do take it up if you want to work on this. Just let me know if you plan to so I know to check out other issues when I do get the time.

[maartenflippo]

Alright then I'll take this up.